The invention relates to a shiftable lens hood for a camera, and more particularly, to a hood for a shiftable taking lens in which effective light rays within the maximum photographing angle of view of the shiftable or perspective control taking lens are not shaded even when the latter is shifted.
As is well known, a lens hood in common use, which is made in a cylindrical form or a prismatic form, is removably mounted on the front end of a taking lens barrel so that effective light rays within the maximum angle of view of a taking lens are not shaded but light rays outside of the maximum angle of view are intercepted. That is, the lens hood in common use is formed so as to exhibit an effective light shading effect only to a specific angle of view adapted to a taking lens barrel on which the lens hood is mounted. Therefore, when such a lens hood is mounted on a shiftable lens whose maximum angle of view varies in accordance with a shifted position of the lens, effective light rays within the angle of view are shaded or, conversely speaking, undesirable light rays are not intercepted, resulting in a failure of the function of the lens hood. To be more precise,
(1) a lens hood which is effective to shade light rays outside an angle of view for photographing when the taking lens is not shifted, may cause a shading of effective light rays when the taking lens is shifted to increase the maximum angle of image falling within the increased angle of view, resulting in a vignetting on the periphery of a picture plane; and
(2) a lens hood which is effective to shade light rays falling within an angle of view for photographing when the taking lens is shifted may fail to intercept undesirable light rays when the taking lens is shifted in a reduced manner to decrease the maximum angle of view, resulting in a detrimental influence such as a flare, a ghost, or the like in a picture plane.